بسم الله الرحمن الرحيم
(1, 2) If you have bought all the said plots or got them bought with the intention that you shall build house or clinic at another place from the money which you shall get by selling and shall fulfill your needs and your family’s needs with the money, then in such a case zakah shall be wajib on the value of all the plots. On the completion of the year you will have to pay fortieth part of the total value as zakah on all the plots as per their current price. And in case you did not buy the plot with the intention of sale rather you bought it just to build the residential house, clinic and rental house and shop then in such a case no zakah shall be wajib on the value of the plots.
(3) It is not correct to use zakah money in the construction of hospital or mosque or any welfare institution or in any such work where no Shariah tamlik (giving in the possession of a poor) is found. Yes, if the patient in the hospital are eligible to receive zakah then you may give them zakah by giving it in their possession. If there is none eligible for zakah then you should investigate nearby and thus you may also pay your zakah in some religious madrasa if there are students who are eligible to receive zakah.
Allah knows Best!
Darul Uloom Deoband